Perception measurement in clinical trials of schizophrenia: promising paradigms from CNTRICS

Modulation of the neuronal response in human primary visual cortex by re-entrant projections during retinal input processing as manifest in the visual evoked potential

Initial deflections in the visual evoked potential (VEP) reflect the neuronal process of extracting features from the retinal input; a process not modulated by re-entrant projections. Later deflections in the VEP reflect the neuronal process of combining features into an object, a process referred to as 'object closure' and modulated by re-entrant projections. Our earlier work indicated that the VEP reflects independent neuronal responses processing temporal - and spatial luminance contrast and that these responses arise from an interaction between forward and re-entrant input. In this earlier work, changing the temporal luminance contrast property of a stimulus altered its spatial luminance contrast property. We recorded the VEP in 12 volunteers viewing image pairs of a windmill, regular dartboard or an RMS dartboard rotated by either Π/4, Π/2, 3Π/4 or Π radians with respect to each other. The windmill and regular dartboard had identical white to black ratio, while the two dartboards identical contrast edges per unit area. Rotation varied temporal luminance contrast of a stimulus without affecting its spatial luminance contrast. N75, P100, N135 and P240 amplitude and latency were compared and a source localisation and temporal frequency analysis performed. P100 amplitude signals a neuronal response processing temporal luminance contrast that is modulated by re-entrant projections with fast axonal conduction velocities. N135 and P240 signal the neuronal response processing spatial luminance contrast and is modulated by re-entrant projections with slow axonal conduction velocities. The dorsal stream is interconnected by fast axonal conduction velocities, the ventral stream by slow axonal conduction velocities.

An α7 nAChR approach for the baseline-dependent modulation of deviance detection in schizophrenia: A pilot study assessing the combined effect of CDP-choline and galantamine

BACKGROUND

Cognitive operations including pre-attentive sensory processing are markedly impaired in patients with schizophrenia (SCZ) but evidence significant interindividual heterogeneity, which moderates treatment response with nicotinic acetylcholine receptor (nAChR) agonists. Previous studies in healthy volunteers have shown baseline-dependency effects of the α7 nAChR agonist cytidine 5'-diphosphocholine (CDP-choline) administered alone and in combination with a nicotinic allosteric modulator (galantamine) on auditory deviance detection measured with the mismatch negativity (MMN) event-related potential (ERP).

AIM

The objective of this pilot study was to assess the acute effect of this combined α7 nAChR-targeted treatment (CDP-choline/galantamine) on speech MMN in patients with SCZ (N = 24) stratified by baseline MMN responses into low, medium, and high baseline auditory deviance detection subgroups.

METHODS

Patients with a stable diagnosis of SCZ attended two randomized, double-blind, placebo-controlled and counter-balanced testing sessions where they received a placebo or a CDP-choline (500 mg) and galantamine (16 mg) treatment. MMN ERPs were recorded during the presentation of a fast multi-feature speech MMN paradigm including five speech deviants. Clinical measures were acquired before and after treatment administration.

RESULTS

While no main treatment effect was observed, CDP-choline/galantamine significantly increased MMN amplitudes to frequency, duration, and vowel speech deviants in low group individuals. Individuals with higher positive and negative symptom scale negative, general, and total scores expressed the greatest MMN amplitude improvement following CDP-choline/galantamine.

CONCLUSIONS

These baseline-dependent nicotinic effects on early auditory information processing warrant different dosage and repeated administration assessments in patients with low baseline deviance detection levels.

Is there magnocellular facilitation of early neural processes underlying visual word recognition? Evidence from masked repetition priming with ERPs

An influential theory in the field of visual object recognition proposes that it is the fast magnocellular (M) system that facilitates neural processing of spatially more fine-grained information rather the slower parvocellular (P) system. While written words can be considered as a special type of visual objects, it is unknown whether magnocellular facilitation also plays a role in reading. We used a masked priming paradigm that has been shown to result in neural facilitation in visual word processing and tested whether these facilitating effects are mediated by the magnocellular system. In two experiments, we manipulated the influence of magnocellular and parvocellular systems on visual processing of a contextually predictable target character by contrasting high versus low spatial frequency and luminance versus color contrast, respectively. In addition, unchanged (normal) primes were included in both experiments as a manipulation check. As expected, unchanged primes elicited typical repetition effects in the N1, N250 and P3 components of the ERP in both experiments. In the experiment manipulating spatial contrast, we obtained repetition effects only for the N1 component for both M- and P-biased primes. In the luminance versus color contrast experiment, repetition effects were found in N1 and N250 for both M- and P- biased primes. Furthermore, no interactions were found between M-vs. P-biased prime types and repetition. Together these results indicate that M- and P- information contributes jointly to early neural processes underlying visual word recognition.

Cognitive function mediates the relationship between visual contrast sensitivity and functional outcome in schizophrenia

BACKGROUND

Individuals with schizophrenia exhibit deficits in visual contrast processing, though less is known about how these deficits impact neurocognition and functional outcomes. This study investigated effects of contrast sensitivity (CS) on cognition and capacity for independent living in schizophrenia.

METHODS

Participants were 58 patients with schizophrenia (n = 49) and schizoaffective disorder (n = 9). Patients completed a psychophysical paradigm to obtain CS with stimuli consisting of grating patterns of low (0.5 and 1 cycles/degree) and high spatial frequencies (4, 7, 21 cycles/degree). Patients completed the MATRICS Consensus Cognitive Battery and Wechsler Adult Intelligence Scales, Third Edition to assess cognition, and the problem-solving factor of the Independent Living Scales to assess functional capacity. We computed bivariate correlation coefficients for all pairs of variables and tested mediation models with CS to low (CS-LSF) and high spatial frequencies (CS-HSF) as predictors, cognitive measures as mediators, and capacity for independent living as an outcome.

RESULTS

Cognition mediated the relationship between CS and independent living with CS-LSF a stronger predictor than CS-HSF. Mediation effects were strongest for perceptual organization and memory-related domains. In an expanded moderated mediation model, CS-HSF was found to be a significant predictor of independent living through perceptual organization as a mediator and CS-LSF as a moderator of this relationship.

CONCLUSION

CS relates to functional capacity in schizophrenia through neurocognition. These relationships may inform novel visual remediation interventions.

Pictorial size perception in schizophrenia

In this study, we compared visual pictorial size perception between healthy volunteers (CG) and an experimental group (EG) of people diagnosed with schizophrenia. We have been using paintings by Salvador Dalí and Rorschach plates to estimate visual pictorial size perception. In this transversal, ex post facto, and quasi-experimental study, we observed differences between EG and CG. Schizophrenic in-patients perceived sizes about 1.3-fold greater than healthy volunteers (p=0.006), implying that pictorial size perception is altered in some way in schizophrenia. Considering the present and previous results, this measurement of diameter size of first pictorial perception may be a useful estimate of some aspects of perceptual alterations that may be associated with psychotic symptoms in prodromal and acute schizophrenic episodes and other related mental states. Eventually, this may help in preventing people from evolving to acute episodes.

Classification of First-Episode Schizophrenia, Chronic Schizophrenia and Healthy Control Based on Brain Network of Mismatch Negativity by Graph Neural Network

Mismatch negativity (MMN) has been consistently found deficit in schizophrenia, which was considered as a promising biomarker for assessing the impairments in pre-attentive auditory processing. However, the functional connectivity between brain regions based on MMN is not clear. This study provides an in-depth investigation in brain functional connectivity during MMN process among patients with first-episode schizophrenia (FESZ), chronic schizophrenia (CSZ) and healthy control (HC). Electroencephalography (EEG) data of 128 channels is recorded during frequency and duration MMN in 40 FESZ, 40 CSZ patients and 40 matched HC subjects. We reconstruct the cortical endogenous electrical activity from EEG recordings using exact low-resolution electromagnetic tomography and build functional brain networks based on source-level EEG data. Then, graph-theoretic features are extracted from the brain networks with the support vector machine (SVM) to classify FESZ, CSZ and HC groups, since the SVM has good generalization ability and robustness as a universally applicable nonlinear classifier. Furthermore, we introduce the graph neural network (GNN) model to directly learn for the network topology of brain network. Compared to HC, the damaged brain areas of CSZ are more extensive than FESZ, and the damaged area involved the auditory cortex. These results demonstrate the heterogeneity of the impacts of schizophrenia for different disease courses and the association between MMN and the auditory cortex. More importantly, the GNN classification results are significantly better than those of SVM, and hence the EEG-based GNN model of brain networks provides an effective method for discriminating among FESZ, CSZ and HC groups.

No Evidence of Reduced Contrast Sensitivity in Migraine-with-Aura for Large, Narrowband, Centrally Presented Noise-Masked Stimuli

Individuals with migraine aura show differences in visual perception compared to control groups. Measures of contrast sensitivity have suggested that people with migraine aura are less able to exclude external visual noise, and that this relates to higher variability in neural processing. The current study compared contrast sensitivity in migraine with aura and control groups for narrow-band grating stimuli at 2 and 8 cycles/degree, masked by Gaussian white noise. We predicted that contrast sensitivity would be lower in the migraine with aura group at high noise levels. Contrast sensitivity was higher for the low spatial frequency stimuli, and decreased with the strength of the masking noise. We did not, however, find any evidence of reduced contrast sensitivity associated with migraine with aura. We propose alternative methods as a more targeted assessment of the role of neural noise and excitability as contributing factors to migraine aura.

The neural correlates of the visual consciousness in schizophrenia: an fMRI study

In the current literature, two distinct and opposite models are suggested to explain the consciousness disorders in schizophrenia. The first one suggests that consciousness disorders rely on a low-level processing deficit, when the second model suggests that consciousness disorders rely on disruption in the ability to consciously access information, with preserved unconscious processing. The current study aims to understand the mechanisms associated with visual consciousness disorder in order to pave the road that will settle the debate regarding these hypotheses. During a functional magnetic resonance imaging session, 19 healthy participants (HC) and 15 patients with schizophrenia (SCZ) performed a visual detection task to compare the neural substrates associated with the conscious access to the visual inputs. The visual detection threshold was significantly higher in SCZ than in HC [t(32) = 3.37, p = 0.002]. Whole-brain ANOVA demonstrated that around the visual detection threshold patients with SCZ failed to activate a large network of brain areas compared to HC. (1) During conscious vision, HC engaged more the left cuneus and the right occipital cortex than patients with SCZ, (2) during unconscious vision, HC engaged a large network that patients with SCZ failed to activate, and finally, (3) during the access to consciousness process, patients with SCZ failed to activate the anterior cingulate cortex. These results suggest that the consciousness disorders in schizophrenia rely on specific dysfunctions depending on the consciousness stage. The disorders of the conscious vision are associated with dysfunction of occipital areas while the ones associated with unconscious vision rely on a large widespread network. Finally, the conscious access to the visual inputs is impaired by a dysfunction of the anterior cingulate cortex. The current study suggests that none of the two suggested models can explain consciousness disorders in schizophrenia. We suggest that there is an alternative model supporting that the conscious access to visual inputs is due to a disengagement of the supragenual anterior cingulate during the unconscious processing of the visual inputs associated with a sensory deficit.

White Matter Correlates of Hostility and Aggression in the Visuospatial Function Network in Patients With Schizophrenia

Background: Violent acts in patients with schizophrenia are often associated with their hostility and aggression levels. Poor visuospatial processing has been suggested as a possible risk factor of violence in schizophrenia. However, studies investigating the relationship between hostility, aggression, and the visuospatial function have been lacking. Here, we aimed to investigate brain dysconnectivity associated with hostility and aggression in schizophrenia, particularly focusing on the visuospatial function network. Methods: Eighty-eight participants with schizophrenia and 42 healthy controls were enrolled. The visuospatial function network regions of interest were analyzed using Tract-Based Spatial Statistics. The hostility item from the Positive and Negative Syndrome Scale (PANSS), aggressive, and agitated behavior item from the Scale for the Assessment of Positive Symptoms (SAPS), and the Rey Complex Figure Test (R-CFT) were measured. Results: Among the participants with schizophrenia, the SAPS aggressive and agitated behavior scores were significantly correlated with fractional anisotropies (FAs) of the white matter regions in the splenium of the corpus callosum (CC), left posterior thalamic radiations (PTR), and left posterior corona radiata (PCR). Exploratory correlational analysis revealed significant negative correlations between FAs of the splenium of the CC and R-CFT copy and immediate recall scores. In addition, three regions including CC, PTR, and PCR that significantly correlated with the aggression scores showed significant correlations with the total PANSS scores. Conclusion: Our main finding suggests that aggression of patients with schizophrenia may be associated with poor visuospatial ability and underlying white matter dysconnectivity. These may help enhance understanding aggression in patients with schizophrenia.

Structural and Functional Connectivity of Visual Cortex in Schizophrenia and Bipolar Disorder: A Graph-Theoretic Analysis

Visual processing abnormalities in schizophrenia (SZ) are poorly understood, yet predict functional outcomes in the disorder. Bipolar disorder (BD) may involve similar visual processing deficits. Converging evidence suggests that visual processing may be relatively normal at early stages of visual processing such as early visual cortex (EVC), but that processing abnormalities may become more pronounced by mid-level visual areas such as lateral occipital cortex (LO). However, little is known about the connectivity of the visual system in SZ and BD. If the flow of information to, from, or within the visual system is disrupted by reduced connectivity, this could help to explain perceptual deficits. In the present study, we performed a targeted analysis of the structural and functional connectivity of the visual system using graph-theoretic metrics in a sample of 48 SZ, 46 BD, and 47 control participants. Specifically, we calculated parallel measures of local efficiency for EVC and LO from both diffusion weighted imaging data (structural) and resting-state (functional) imaging data. We found no structural connectivity differences between the groups. However, there was a significant group difference in functional connectivity and a significant group-by-region interaction driven by reduced LO connectivity in SZ relative to HC, whereas BD was approximately intermediate to the other 2 groups. We replicated this pattern of results using a different brain atlas. These findings support and extend theoretical models of perceptual dysfunction in SZ, providing a framework for further investigation of visual deficits linked to functional outcomes in SZ and related disorders.

CDP-choline and galantamine, a personalized α7 nicotinic acetylcholine receptor targeted treatment for the modulation of speech MMN indexed deviance detection in healthy volunteers: a pilot study

RATIONALE

The combination of CDP-choline, an α7 nicotinic acetylcholine receptor (α7 nAChR) agonist, with galantamine, a positive allosteric modulator of nAChRs, is believed to counter the fast desensitization rate of the α7 nAChRs and may be of interest for schizophrenia (SCZ) patients. Beyond the positive and negative clinical symptoms, deficits in early auditory prediction-error processes are also observed in SCZ. Regularity violations activate these mechanisms that are indexed by electroencephalography-derived mismatch negativity (MMN) event-related potentials (ERPs) in response to auditory deviance.

OBJECTIVES/METHODS

This pilot study in thirty-three healthy humans assessed the effects of an optimized α7 nAChR strategy combining CDP-choline (500 mg) with galantamine (16 mg) on speech-elicited MMN amplitude and latency measures. The randomized, double-blinded, placebo-controlled, and counterbalanced design with a baseline stratification method allowed for assessment of individual response differences.

RESULTS

Increases in MMN generation mediated by the acute CDP-choline/galantamine treatment in individuals with low baseline MMN amplitude for frequency, intensity, duration, and vowel deviants were revealed.

CONCLUSIONS

These results, observed primarily at temporal recording sites overlying the auditory cortex, implicate α7 nAChRs in the enhancement of speech deviance detection and warrant further examination with respect to dysfunctional auditory deviance processing in individuals with SCZ.

Development and Evaluation of a Visual Remediation Intervention for People with Schizophrenia

It is now well documented that schizophrenia is associated with impairments in visual processing at all levels of vision, and that these disturbances are related to deficits in multiple higher-level cognitive and social cognitive functions. Visual remediation methods have been slow to appear in the literature as a potential treatment strategy to target these impairments, however, in contrast to interventions that aim to improve auditory and higher cognitive functions in schizophrenia. In this report, we describe a National Institute of Mental Health (NIMH)-funded R61/R33 grant that uses a phased approach to optimize and evaluate a novel visual remediation intervention for people with schizophrenia. The goals of this project are: (1) in the R61 phase, to establish the optimal components and dose (number of sessions) of a visual remediation intervention from among two specific visual training strategies (and their combination) for improving low and mid-level visual functions in schizophrenia; and (2) in the R33 phase, to determine the extent to which the optimal intervention improves not only visual processing but also higher-level cognitive and role functions. Here we present the scientific background for and innovation of the study, along with our methods, hypotheses, and preliminary data. The results of this study will help determine the utility of this novel intervention approach for targeting visual perceptual, cognitive, and functional impairments in schizophrenia.

Adolescent Cannabis Use and Conduct Problems: The Mediating Influence of Callous-Unemotional Traits

Cannabis use has been linked to an increased risk of engaging in conduct problem behaviors. However, little existing research has considered intervening processes and shared risk factors that may contribute to this association. The current investigation examines whether callous-unemotional traits, which have shown associations with adolescent cannabis use and conduct problem development, may exhibit a mediating influence on this relationship. Using a longitudinal cohort of youth (n = 390) at increased risk for escalating in their use of cannabis, we found that baseline cannabis use (age~15) was associated with higher levels of trait-like conduct problems (ages~16 & 17), even after controlling for important autoregressive and cross-lagged effects, along with a number of other shared risk factors (e.g., co-occuring substance use, age, sex). Findings also revealed that callous-unemotional traits partially mediated this relationship, with the hypothesized model accounting for approximately one-third of the variance in the conduct problem outcome (R2=.34). These results indicate that callous-unemotional traits may play an important intermediary role in the association between cannabis use and the development of problem behaviors.

The abiding relevance of mouse models of rare mutations to psychiatric neuroscience and therapeutics

Studies using powerful family-based designs aided by large scale case-control studies, have been instrumental in cracking the genetic complexity of the disease, identifying rare and highly penetrant risk mutations and providing a handle on experimentally tractable model systems. Mouse models of rare mutations, paired with analysis of homologous cognitive and sensory processing deficits and state-of-the-art neuroscience methods to manipulate and record neuronal activity have started providing unprecedented insights into pathogenic mechanisms and building the foundation of a new biological framework for understanding mental illness. A number of important principles are emerging, namely that degradation of the computational mechanisms underlying the ordered activity and plasticity of both local and long-range neuronal assemblies, the building blocks necessary for stable cognition and perception, might be the inevitable consequence and the common point of convergence of the vastly heterogeneous genetic liability, manifesting as defective internally- or stimulus-driven neuronal activation patterns and triggering the constellation of schizophrenia symptoms. Animal models of rare mutations have the unique potential to help us move from "which" (gene) to "how", "where" and "when" computational regimes of neural ensembles are affected. Linking these variables should improve our understanding of how symptoms emerge and how diagnostic boundaries are established at a circuit level. Eventually, a better understanding of pathophysiological trajectories at the level of neural circuitry in mice, aided by basic human experimental biology, should guide the development of new therapeutics targeting either altered circuitry itself or the underlying biological pathways.

Examining motion speed processing in schizophrenia using the flash lag illusion

Research on visual perception in schizophrenia suggests a deficit in motion processing. Specifically, difficulties with discriminating motion speed are commonly reported. However, speed discrimination tasks typically require participants to make judgments about the difference between two stimuli in a two-interval forced choice (2IFC) task. Such tasks not only tap into speed processing mechanisms, but also rely on higher executive functioning including working memory and attention which has been shown to be compromised in schizophrenia. We used the Flash Lag illusion to examine speed processing in patients with schizophrenia. Based on previous research showing a strong dependence between motion speed and the illusion magnitude, we expected a deficit in speed processing to alter this relationship. A motion processing deficit in patients would also predict overall reductions in perceived lag. We found the magnitude and speed dependence of the Flash Lag illusion to be similar in patients and controls. Together, the findings suggest no general abnormality in motion speed processing in schizophrenia.

Sensory processing deficiencies in patients with borderline personality disorder who experience auditory verbal hallucinations

Auditory verbal hallucinations (AVH) are common in patients with borderline personality disorder (BPD). We examined two candidate mechanisms of AVH in patients with BPD, suggested to underlie sensory processing systems that contribute to psychotic symptoms in patients with schizophrenia; sensory gating (P50 ratio and P50 difference) and change detection (mismatch negativity; MMN). Via electroencephalographic recordings P50 amplitude, P50 ratio, P50 difference and MMN amplitude were compared between 23 borderline patients with and 25 without AVH, and 26 healthy controls. Borderline patients with AVH had a significantly lower P50 difference compared with healthy controls, whereas no difference was found between borderline patients without AVH and healthy controls. The groups did not differ on MMN amplitude. The impaired sensory gating in patients with borderline personality disorder who experience AVH implies that P50 sensory gating deficiencies may underlie psychotic vulnerability in this specific patient group. Patients with borderline personality disorder with or without AVH did not have problems with auditory change detection. This may explain why they are spared from the poor outcome associated with negative symptoms and symptoms of disorganization in patients with chronic schizophrenia.

Mechanisms of Spatiotemporal Selectivity in Cortical Area MT

Cortical sensory neurons are characterized by selectivity to stimulation. This selectivity was originally viewed as a part of the fundamental "receptive field" characteristic of neurons. This view was later challenged by evidence that receptive fields are modulated by stimuli outside of the classical receptive field. Here, we show that even this modified view of selectivity needs revision. We measured spatial frequency selectivity of neurons in cortical area MT of alert monkeys and found that their selectivity strongly depends on luminance contrast, shifting to higher spatial frequencies as contrast increases. The changes of preferred spatial frequency are large at low temporal frequency, and they decrease monotonically as temporal frequency increases. That is, even interactions among basic stimulus dimensions of luminance contrast, spatial frequency, and temporal frequency strongly influence neuronal selectivity. This dynamic nature of neuronal selectivity is inconsistent with the notion of stimulus preference as a stable characteristic of cortical neurons.

Neurocognitive and Perceptual Processing in Genetic Mouse Models of Schizophrenia: Emerging Lessons

During the past two decades, the number of animal models of psychiatric disorders has grown exponentially. Of these, genetic animal models that are modeled after rare but highly penetrant mutations hold great promise for deciphering critical molecular, synaptic, and neurocircuitry deficits of major psychiatric disorders, such as schizophrenia. Animal models should aim to focus on core aspects rather than capture the entire human disease. In this context, animal models with strong etiological validity, where behavioral and neurophysiological phenotypes and the features of the disease being modeled are in unambiguous homology, are being used to dissect both elementary and complex cognitive and perceptual processing deficits present in psychiatric disorders at the level of neurocircuitry, shedding new light on critical disease mechanisms. Recent progress in neuroscience along with large-scale initiatives that propose a consistent approach in characterizing these deficits across different laboratories will further enhance the efficacy of these studies that will ultimately lead to identifying new biological targets for drug development.

Poorer Search Efficiency in Healthy Young Adults With High Schizotypal Personality Traits

Perceptual organization (PO) difficulties have repeatedly been reported in people with schizophrenia, and in healthy individuals with high levels of schizotypy traits, who are at increased risk for schizophrenia. In particular, poor performance on the Embedded Figures Test (EFT) has been interpreted as an atypically strong preference for global over local processing, even though these processes cannot be clearly disambiguated on this test. Here we use two separate versions of the Radial Frequency Search Task (RFST), a new index of PO abilities, to selectively investigate global and local processing of shape information in trait schizotypy. Schizotypy traits were assessed using the Wisconsin Schizotypy Scales-Brief. Individuals selected for high and low levels of positive schizotypy [assessed with the Wisconsin Schizotypy Scales-Brief Perceptual Aberration (PAb) scale] completed the EFT, along with the Global RFST and the Local RFST, all of which require participants to find a target shape amongst distractor elements. The High PAb group (n = 83) were less efficient (i.e., reactions times slowed more as the set size increased) than the Low PAb group (n = 146) on the Global RFST (significant group differences for Target Absent conditions only), but not the Local RFST. High and Low PAb groups also differed on other schizotypy traits, so the specificity of the results to positive schizotypy cannot be assured. Unexpectedly, no group differences were observed on the EFT; however, there was a small, but significant, positive correlation between RFST search efficiency and EFT performance, indicating that they shared some common processes. Overall, the pattern of results suggests that global (but not local) processing difficulties may be contributing to the poorer perceptual organization observed in groups with high levels of schizotypy traits. In addition, the confinement of this result to the Target Absent condition suggests that the underlying mechanism involves differences in decisional processes on the RFST between high and low schizotypy groups. The RFST shows promise as a useful tool for measuring specific perceptual organization abilities in non-clinical, and potentially clinical, samples.

Shades of grey; Assessing the contribution of the magno- and parvocellular systems to neural processing of the retinal input in the human visual system from the influence of neural population size and its discharge activity on the VEP

INTRODUCTION

Retinal input processing in the human visual system involves a phasic and tonic neural response. We investigated the role of the magno- and parvocellular systems by comparing the influence of the active neural population size and its discharge activity on the amplitude and latency of four VEP components.

METHOD

We recorded the scalp electric potential of 20 human volunteers viewing a series of dartboard images presented as a pattern reversing and pattern on-/offset stimulus. These patterns were designed to vary both neural population size coding the temporal- and spatial luminance contrast property and the discharge activity of the population involved in a systematic manner.

RESULTS

When the VEP amplitude reflected the size of the neural population coding the temporal luminance contrast property of the image, the influence of luminance contrast followed the contrast response function of the parvocellular system. When the VEP amplitude reflected the size of the neural population responding to the spatial luminance contrast property the image, the influence of luminance contrast followed the contrast response function of the magnocellular system. The latencies of the VEP components examined exhibited the same behavior across our stimulus series.

CONCLUSIONS

This investigation demonstrates the complex interplay of the magno- and parvocellular systems on the neural response as captured by the VEP. It also demonstrates a linear relationship between stimulus property, neural response, and the VEP and reveals the importance of feedback projections in modulating the ongoing neural response. In doing so, it corroborates the conclusions of our previous study.

Cortical Thickness of Functionally Defined Visual Areas in Schizophrenia and Bipolar Disorder

Patients with schizophrenia show specific abnormalities in visual perception, and patients with bipolar disorder may have related perceptual deficits. During tasks that highlight perceptual dysfunction, patients with schizophrenia show abnormal activity in visual brain areas, including the lateral occipital complex (LOC) and early retinotopic cortex. It is unclear whether the anatomical structure of those visual areas is atypical in schizophrenia and bipolar disorder. In members of those two patient groups and healthy controls, we localized LOC and early retinotopic cortex individually for each participant using functional magnetic resonance imaging (MRI), then measured the thickness of those regions of interest using structural MRI scans. In both regions, patients with schizophrenia had the thinnest cortex, controls had the thickest cortex, and bipolar patients had intermediate cortical thickness. A control region, motor cortex, did not show this pattern of group differences. The thickness of each visual region of interest was significantly correlated with performance on a visual object masking task, but only in schizophrenia patients. These findings suggest an anatomical substrate for visual processing abnormalities that have been found with both neural and behavioral measures in schizophrenia and other severe mental illnesses.

Spatial Frequency Selectivity Is Impaired in Dopamine D2 Receptor Knockout Mice

Dopamine is a neurotransmitter implicated in several brain functions, including vision. In the present study, we investigated the impacts of the lack of D2 dopamine receptors on the structure and function of the primary visual cortex (V1) of D2-KO mice using optical imaging of intrinsic signals. Retinotopic maps were generated in order to measure anatomo-functional parameters such as V1 shape, cortical magnification factor, scatter, and ocular dominance. Contrast sensitivity and spatial frequency selectivity (SF) functions were computed from responses to drifting gratings. When compared to control mice, none of the parameters of the retinotopic maps were affected by D2 receptor loss of function. While the contrast sensitivity function of D2-KO mice did not differ from their wild-type counterparts, SF selectivity function was significantly affected as the optimal SF and the high cut-off frequency (p < 0.01) were higher in D2-KO than in WT mice. These findings show that the lack of function of D2 dopamine receptors had no influence on cortical structure whereas it had a significant impact on the spatial frequency selectivity and high cut-off. Taken together, our results suggest that D2 receptors play a specific role on the processing of spatial features in early visual cortex while they do not seem to participate in its development.

Using EEG-Guided Basket and Umbrella Trials in Psychiatry: A Precision Medicine Approach for Cognitive Impairment in Schizophrenia

Due to advances over the last several decades, many fields of medicine are moving toward a precision medicine approach where treatments are tailored to nuanced patient factors. While in some disciplines these innovations are commonplace leading to unique biomarker-guided experimental medicine trials, there are no such analogs in psychiatry. In this brief review, we will overview two unique biomarker-guided trial designs for future use in psychiatry: basket and umbrella trials. We will illustrate how such trials could be useful in psychiatry using schizophrenia as a candidate illness, the EEG measure mismatch negativity as the candidate biomarker, and cognitive impairment as the target disease dimension.

Stimuli to differentiate the neural response at successive stages of visual processing using the VEP from human visual cortex

BACKGROUND

Clarifying the enigmatic relationship between stimulus property, neural response and the evoked potential is essential if non-invasive functional imaging is to make a meaningful contribution to the understanding of how maturational or degenerative processes influence brain activity. Visual cortex has proven a favourite target to elucidate this relationship. However, to date most studies involving the visual system have yielded inconsistent results or have been strongly criticised.

NEW METHOD

We developed a set of three visual stimuli, two of which either had the same low- or high spatial frequency characteristic. Adult volunteers viewed these as pattern reversing stimuli while the scalp electric potential was recorded using a 10-10 array of electrodes.

RESULTS

Established processing mechanisms of the primate visual system enabled us to link the amplitude of the N75 and P100 to the size of the neural population processing the temporal luminance contrast, and the amplitude of the N135 and P240 to the size of the neural processing the spatial luminance contrast in our stimuli. Calculating the distribution of current source density enabled us to identify the neural source of each VEP component.

CONCLUSIONS

Demonstrating a direct relationship between the temporal- and spatial luminance contrast properties of our stimuli and the size of the neural population involved provides a better understanding of the nature of the relationship between stimulus property, neural response and the VEP. It also shows that EEG can contribute in a significant manner to the study of the influence of maturational or degenerative processes on brain activity.

Linking optic radiation volume to visual perception in schizophrenia and bipolar disorder

People with schizophrenia typically show visual processing deficits on masking tasks and other performance-based measures, while people with bipolar disorder may have related deficits. The etiology of these deficits is not well understood. Most neuroscientific studies of perception in schizophrenia and bipolar disorder have focused on visual processing areas in the cerebral cortex, but perception also depends on earlier components of the visual system that few studies have examined in these disorders. Using diffusion weighted imaging (DWI), we investigated the structure of the primary sensory input pathway to the cortical visual system: the optic radiations. We used probabilistic tractography to identify the optic radiations in 32 patients with schizophrenia, 31 patients with bipolar disorder, and 30 healthy controls. The same participants also performed a visual masking task outside the scanner. We characterized the optic radiations with three structural measures: fractional anisotropy, mean diffusivity, and tract volume. We did not find significant differences in those structural measures across groups. However, we did find a significant correlation between the volume of the optic radiations and visual masking thresholds that was unique to the schizophrenia group and explained variance in masking performance above and beyond that previously accounted for by differences in visual cortex. Thus, individual differences in the volume of the optic radiations explained more variance in visual masking performance in the schizophrenia group than the bipolar or control groups. This suggests that individual differences in the structure of the subcortical visual system have an important influence on visual processing in schizophrenia.

Sustaining attention to simple visual tasks: a central deficit in schizophrenia? A systematic review

Impairments in sustained attention, that is, the ability to achieve and maintain the focus of cognitive activity on a given stimulation source or task, have been described as central to schizophrenia. Today, sustained attention deficit is still considered as a hallmark of schizophrenia. Nevertheless, current findings on this topic are not consistent. To clarify these findings, we attempt to put these results into perspective according to the type of assessment (i.e., overall and over time assessment), the participants' characteristics (i.e., clinical and demographic characteristics), and the paradigms (i.e., traditionally formatted tasks, go/no-go tasks, and the sustained attention task) and measures used. Two types of assessment lead to opposite findings; they do not evaluate sustained attention the same way. Studies using overall assessments of sustained attention ability tend to reveal a deficit, whereas studies using over time assessments do not. Therefore, further research is needed to investigate the underlying cognitive control mechanisms of changes in sustained attention in schizophrenia.

Assessing neural tuning for object perception in schizophrenia and bipolar disorder with multivariate pattern analysis of fMRI data

Introduction

Deficits in visual perception are well-established in schizophrenia and are linked to abnormal activity in the lateral occipital complex (LOC). Related deficits may exist in bipolar disorder. LOC contains neurons tuned to object features. It is unknown whether neural tuning in LOC or other visual areas is abnormal in patients, contributing to abnormal perception during visual tasks. This study used multivariate pattern analysis (MVPA) to investigate perceptual tuning for objects in schizophrenia and bipolar disorder.

Methods

Fifty schizophrenia participants, 51 bipolar disorder participants, and 47 matched healthy controls completed five functional magnetic resonance imaging (fMRI) runs of a perceptual task in which they viewed pictures of four different objects and an outdoor scene. We performed classification analyses designed to assess the distinctiveness of activity corresponding to perception of each stimulus in LOC (a functionally localized region of interest). We also performed similar classification analyses throughout the brain using a searchlight technique. We compared classification accuracy and patterns of classification errors across groups.

Results

Stimulus classification accuracy was significantly above chance in all groups in LOC and throughout visual cortex. Classification errors were mostly within-category confusions (e.g., misclassifying one chair as another chair). There were no group differences in classification accuracy or patterns of confusion.

Conclusions

The results show for the first time MVPA can be used successfully to classify individual perceptual stimuli in schizophrenia and bipolar disorder. However, the results do not provide evidence of abnormal neural tuning in schizophrenia and bipolar disorder.

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Abnormal visual perception exists in schizophrenia and, likely, bipolar disorder

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Neural processing abnormalities underlying those deficits are not well understood

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We used multivariate analyses of fMRI data to assess patients' visual processing

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We establish for the first time that such methods work well in these patient groups

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The analyses did not show group differences in neural processing of visual stimuli

Enhanced brain responses to color during smooth-pursuit eye movements

Eye movements alter visual perceptions in a number of ways. During smooth-pursuit eye movements, previous studies reported decreased detection threshold for colored stimuli and for high-spatial-frequency luminance stimuli, suggesting a boost in the parvocellular system. The present study investigated the underlying neural mechanism using EEG in human participants. Participants followed a moving target with smooth-pursuit eye movements while steady-state visually evoked potentials (SSVEPs) were elicited by equiluminant red-green flickering gratings in the background. SSVEP responses to colored gratings were 18.9% higher during smooth pursuit than during fixation. There was no enhancement of SSVEPs by smooth pursuit when the flickering grating was defined by luminance instead of color. This result provides physiological evidence that the chromatic response in the visual system is boosted by the execution of smooth-pursuit eye movements in humans. Because the response improvement is thought to be the result of an improved response in the parvocellular system, SSVEPs to equiluminant stimuli could provide a direct test of parvocellular signaling, especially in populations where collecting an explicit behavioral response from the participant is not feasible.NEW & NOTEWORTHY We constantly move our eyes when we explore the world. Eye movements alter visual perception in various ways. The smooth-pursuit eye movements have been shown to boost color sensitivity. We recorded steady-state visually evoked potentials to equiluminant chromatic flickering stimuli and observed increased steady-state visually evoked potentials when participants smoothly pursued a moving target compared with when they maintained fixation. This work provides direct neurophysiological evidence for the parvocellular boost by smooth-pursuit eye movements in humans.

Symptomatic thinking: the current state of Phase III and IV clinical trials for cognition in schizophrenia

Research indicates that relieving the cognitive and negative symptoms of schizophrenia is crucial for improving patient quality of life. However effective pharmacotherapies for cognitive and negative symptoms do not currently exist. A review of ongoing Phase III clinical trials indicates that, despite numerous compounds being investigated for cognition in schizophrenia, few are actually novel and most are not backed by empirically driven preclinical research efforts. Based on these trials, and a general disinvestment in development of novel therapies for schizophrenia, the likelihood of a major advancement in treating cognitive differences in schizophrenia does not look promising. Possible ways in which the remaining resources for development of novel treatment for schizophrenia can best be leveraged are discussed.

[Functional examinations of visual channels: physiological basis]

In this paper, technical details of visual evoked potentials (VEP) assessment and pattern electroretinography (PERG) are reviewed. Both methods are used to perform an objective functional examination of visual channels and to clarify the level, at which they have been damaged. Contributions of parvo- (P), magno- (M) and koniocellular (K) systems to the morphology of PERG and VEP responses are discussed with account to test conditions, selectively supportive of the activity of particular cell populations. The review analyzes the physiological role of such stimulation parameters as brightness and color contrast of the pattern elements as well as spatial and temporal frequency in detecting dysfunction of color channels and mistuning of the P- and M- pathways. Different times taken for neuronal integration and signal conduction along the M- and P- pathways determine the timing of the P- and M- VEP components, allowing us to judge their contribution to VEP morphology from the same recording.

The temporal frequency tuning of continuous flash suppression reveals peak suppression at very low frequencies

Continuous flash suppression (CFS) is a psychophysical technique where a rapidly changing Mondrian pattern viewed by one eye suppresses the target in the other eye for several seconds. Despite the widespread use of CFS to study unconscious visual processes, the temporal tuning of CFS suppression is currently unknown. In the present study we used spatiotemporally filtered dynamic noise as masking stimuli to probe the temporal characteristics of CFS. Surprisingly, we find that suppression in CFS peaks very prominently at approximately 1 Hz, well below the rates typically used in CFS studies (10 Hz or more). As well as a strong bias to low temporal frequencies, CFS suppression is greater for high spatial frequencies and increases with increasing masker contrast, indicating involvement of parvocellular/ventral mechanisms in the suppression process. These results are reminiscent of binocular rivalry, and unifies two phenomenon previously thought to require different explanations.

Reduced Prepulse Inhibition as a Biomarker of Schizophrenia

The startle response is composed by a set of reflex behaviors intended to prepare the organism to face a potentially relevant stimulus. This response can be modulated by several factors as, for example, repeated presentations of the stimulus (startle habituation), or by previous presentation of a weak stimulus (Prepulse Inhibition [PPI]). Both phenomena appear disrupted in schizophrenia that is thought to reflect an alteration in dopaminergic and glutamatergic neurotransmission. In this paper we analyze whether the reported deficits are indicating a transient effect restricted to the acute phase of the disease, or if it reflects a more general biomarker or endophenotype of the disorder. To this end, we measured startle responses in the same set of thirteen schizophrenia patients with a cross-sectional design at two periods: 5 days after hospital admission and 3 months after discharge. The results showed that both startle habituation and PPI were impaired in the schizophrenia patients at the acute stage as compared to a control group composed by 13 healthy participants, and that PPI but not startle habituation remained disrupted when registered 3 months after the discharge. These data point to the consideration of PPI, but not startle habituation, as a schizophrenia biomarker.

Contextual processing in unpredictable auditory environments: the limited resource model of auditory refractoriness in the rhesus

Auditory refractoriness refers to the finding of smaller electroencephalographic (EEG) responses to tones preceded by shorter periods of silence. To date, its physiological mechanisms remain unclear, limiting the insights gained from findings of abnormal refractoriness in individuals with schizophrenia. To resolve this roadblock, we studied auditory refractoriness in the rhesus, one of the most important animal models of auditory function, using grids of up to 32 chronically implanted cranial EEG electrodes. Four macaques passively listened to sounds whose identity and timing was random, thus preventing animals from forming valid predictions about upcoming sounds. Stimulus onset asynchrony ranged between 0.2 and 12.8 s, thus encompassing the clinically relevant timescale of refractoriness. Our results show refractoriness in all 8 previously identified middle- and long-latency components that peaked between 14 and 170 ms after tone onset. Refractoriness may reflect the formation and gradual decay of a basic sensory memory trace that may be mirrored by the expenditure and gradual recovery of a limited physiological resource that determines generator excitability. For all 8 components, results were consistent with the assumption that processing of each tone expends ∼65% of the available resource. Differences between components are caused by how quickly the resource recovers. Recovery time constants of different components ranged between 0.5 and 2 s. This work provides a solid conceptual, methodological, and computational foundation to dissect the physiological mechanisms of auditory refractoriness in the rhesus. Such knowledge may, in turn, help develop novel pharmacological, mechanism-targeted interventions.

Atypical visual and somatosensory adaptation in schizophrenia-spectrum disorders

Neurophysiological investigations in patients with schizophrenia consistently show early sensory processing deficits in the visual system. Importantly, comparable sensory deficits have also been established in healthy first-degree biological relatives of patients with schizophrenia and in first-episode drug-naive patients. The clear implication is that these measures are endophenotypic, related to the underlying genetic liability for schizophrenia. However, there is significant overlap between patient response distributions and those of healthy individuals without affected first-degree relatives. Here we sought to develop more sensitive measures of sensory dysfunction in this population, with an eye to establishing endophenotypic markers with better predictive capabilities. We used a sensory adaptation paradigm in which electrophysiological responses to basic visual and somatosensory stimuli presented at different rates (ranging from 250 to 2550 ms interstimulus intervals, in blocked presentations) were compared. Our main hypothesis was that adaptation would be substantially diminished in schizophrenia, and that this would be especially prevalent in the visual system. High-density event-related potential recordings showed amplitude reductions in sensory adaptation in patients with schizophrenia (N=15 Experiment 1, N=12 Experiment 2) compared with age-matched healthy controls (N=15 Experiment 1, N=12 Experiment 2), and this was seen for both sensory modalities. At the individual participant level, reduced adaptation was more robust for visual compared with somatosensory stimulation. These results point to significant impairments in short-term sensory plasticity across sensory modalities in schizophrenia. These simple-to-execute measures may prove valuable as candidate endophenotypes and will bear follow-up in future work.

The Core Brain Region for Face Processing in Schizophrenia Lacks Face Selectivity

BACKGROUND

Face perception impairment in schizophrenia has long been recognized. However, brain mechanisms underlying this socially important perceptual deficit are not well understood. Previous magnetic resonance imaging (MRI) studies have shown that patients have altered structure in brain regions responsible for processing face information, but functional properties of these brain regions are not clearly determined. A key functional property of the face-processing system--face selectivity--has yet to be evaluated in schizophrenia.

METHODS

We used functional MRI (fMRI) to examine face selectivity of 3 core face-processing regions--fusiform face area (FFA), occipital face area (OFA), and superior temporal sulcus (STS)--in schizophrenia patients (n = 24) and healthy controls (n = 23). To disassociate face-specific processing from general perceptual processing, we compared cortical activations during performance of perceptually equated face and tree detection tasks.

RESULTS

Activation levels of the 3 putative face-processing regions during face detection did not differ between patients and controls, being similar for FFA and OFA and absent for STS. However, face selectivity, indexed by the difference in cortical activation between face and tree detection, was significantly reduced in patients for FFA, especially for low-contrast stimuli. FFA activation and perceptual performance during face detection were associated in patients.

CONCLUSIONS

These results show a lack of face-specific processing in the schizophrenic brain region presumably subserving face perception. This finding suggests boosting visual salience of face images as a potential therapeutic venue for improving face perception in this psychiatric disorder.

Deficient cortical face-sensitive N170 responses and basic visual processing in schizophrenia

BACKGROUND

Face detection, an ability to identify a visual stimulus as a face, is impaired in patients with schizophrenia. It is unclear whether impaired face processing in this psychiatric disorder results from face-specific domains or stems from more basic visual domains. In this study, we examined cortical face-sensitive N170 response in schizophrenia, taking into account deficient basic visual contrast processing.

METHODS

We equalized visual contrast signals among patients (n=20) and controls (n=20) and between face and tree images, based on their individual perceptual capacities (determined using psychophysical methods). We measured N170, a putative temporal marker of face processing, during face detection and tree detection.

RESULTS

In controls, N170 amplitudes were significantly greater for faces than trees across all three visual contrast levels tested (perceptual threshold, two times perceptual threshold and 100%). In patients, however, N170 amplitudes did not differ between faces and trees, indicating diminished face selectivity (indexed by the differential responses to face vs. tree).

CONCLUSION

These results indicate a lack of face-selectivity in temporal responses of brain machinery putatively responsible for face processing in schizophrenia. This neuroimaging finding suggests that face-specific processing is compromised in this psychiatric disorder.

Visual and associated affective processing of face information in schizophrenia: A selective review

Perception of facial features is crucial in social life. In past decades, extensive research showed that the ability to perceive facial emotion expression was compromised in schizophrenia patients. Given that face perception involves visual/cognitive and affective processing, the roles of these two processing domains in the compromised face perception in schizophrenia were studied and discussed, but not clearly defined. One particular issue was whether face-specific processing is implicated in this psychiatric disorder. Recent investigations have probed into the components of face perception processes such as visual detection, identity recognition, emotion expression discrimination and working memory conveyed from faces. Recent investigations have further assessed the associations between face processing and basic visual processing and between face processing and social cognitive processing such as Theory of Mind. In this selective review, we discuss the investigative findings relevant to the issues of cognitive and affective association and face-specific processing. We highlight the implications of multiple processing domains and face-specific processes as potential mechanisms underlying compromised face perception in schizophrenia. These findings suggest a need for a domain-specific therapeutic approach to the improvement of face perception in schizophrenia.

A Hierarchical Generative Framework of Language Processing: Linking Language Perception, Interpretation, and Production Abnormalities in Schizophrenia

Language and thought dysfunction are central to the schizophrenia syndrome. They are evident in the major symptoms of psychosis itself, particularly as disorganized language output (positive thought disorder) and auditory verbal hallucinations (AVHs), and they also manifest as abnormalities in both high-level semantic and contextual processing and low-level perception. However, the literatures characterizing these abnormalities have largely been separate and have sometimes provided mutually exclusive accounts of aberrant language in schizophrenia. In this review, we propose that recent generative probabilistic frameworks of language processing can provide crucial insights that link these four lines of research. We first outline neural and cognitive evidence that real-time language comprehension and production normally involve internal generative circuits that propagate probabilistic predictions to perceptual cortices - predictions that are incrementally updated based on prediction error signals as new inputs are encountered. We then explain how disruptions to these circuits may compromise communicative abilities in schizophrenia by reducing the efficiency and robustness of both high-level language processing and low-level speech perception. We also argue that such disruptions may contribute to the phenomenology of thought-disordered speech and false perceptual inferences in the language system (i.e., AVHs). This perspective suggests a number of productive avenues for future research that may elucidate not only the mechanisms of language abnormalities in schizophrenia, but also promising directions for cognitive rehabilitation.

The NEWMEDS rodent touchscreen test battery for cognition relevant to schizophrenia

RATIONALE

The NEWMEDS initiative (Novel Methods leading to New Medications in Depression and Schizophrenia, http://www.newmeds-europe.com ) is a large industrial-academic collaborative project aimed at developing new methods for drug discovery for schizophrenia. As part of this project, Work package 2 (WP02) has developed and validated a comprehensive battery of novel touchscreen tasks for rats and mice for assessing cognitive domains relevant to schizophrenia.

OBJECTIVES

This article provides a review of the touchscreen battery of tasks for rats and mice for assessing cognitive domains relevant to schizophrenia and highlights validation data presented in several primary articles in this issue and elsewhere.

METHODS

The battery consists of the five-choice serial reaction time task and a novel rodent continuous performance task for measuring attention, a three-stimulus visual reversal and the serial visual reversal task for measuring cognitive flexibility, novel non-matching to sample-based tasks for measuring spatial working memory and paired-associates learning for measuring long-term memory.

RESULTS

The rodent (i.e. both rats and mice) touchscreen operant chamber and battery has high translational value across species due to its emphasis on construct as well as face validity. In addition, it offers cognitive profiling of models of diseases with cognitive symptoms (not limited to schizophrenia) through a battery approach, whereby multiple cognitive constructs can be measured using the same apparatus, enabling comparisons of performance across tasks.

CONCLUSION

This battery of tests constitutes an extensive tool package for both model characterisation and pre-clinical drug discovery.

Opposing effects of glutamatergic and GABAergic pharmacological manipulations on a visual perception task with relevance to schizophrenia

RATIONALE

Numerous psychiatric disorders and neurodegenerative diseases have been associated with differences in visual perception, and it has been proposed that the treatment of these differences may represent a novel means to treat disorders like schizophrenia. Unfortunately, few methods exist to study visual perception in pre-clinical species.

OBJECTIVE

The purpose of the present study was to adapt a task of visual integration by proximity with relevance to schizophrenia to a rodent touchscreen environment to determine the effects of glutamatergic and GABAergic compounds. In this way, we could evaluate the effects of common models of cognitive impairment, as well as the effects of net excitation versus inhibition, on a task of visual integration.

METHOD

Rats were trained to perform a visual discrimination where the stimuli were composed of rows of dots differing only in there horizontal and vertical proximity. Once stable performance had been achieved, animals were tested under the influence of glutamatergic or GABAergic drugs (ketamine, MK-801, PCP, memantine, chlordiazepoxide, or diazepam) while attempting to perform a visual discrimination with altered stimuli.

RESULTS

Ketamine appeared to impair perceptual grouping in this paradigm, while the GABA agonist chlordiazepoxide enhanced grouping even in the presence of non-selective effects.

CONCLUSIONS

In general, these findings support the theory that NMDA antagonists may disrupt visual grouping by proximity and highlight a potential beneficial effect of enhanced GABA activity in perception. However, additional research will be required to confirm the stimulus selectivity of this effect, and the clinical significance of this approach.

Cortical contributions to impaired contour integration in schizophrenia

OBJECTIVES

Visual perceptual organization impairments in schizophrenia (SCZ) are well established, but their neurobiological bases are not. The current study used the previously validated Jittered Orientation Visual Integration (JOVI) task, along with fMRI, to examine the neural basis of contour integration (CI), and its impairment in SCZ. CI is an aspect of perceptual organization in which multiple distinct oriented elements are grouped into a single continuous boundary or shape.

METHODS

On the JOVI, five levels of orientational jitter were added to non-contiguous closed contour elements embedded in background noise to progressively increase the difficulty in perceiving contour elements as left- or right-pointing ovals. Multi-site fMRI data were analyzed for 56 healthy control subjects and 47 people with SCZ.

RESULTS

SCZ patients demonstrated poorer CI, and this was associated with increased activation in regions involved in global shape processing and visual attention, namely the lateral occipital complex and superior parietal lobules. There were no brain regions where controls demonstrated more activation than patients.

CONCLUSIONS

CI impairment in this sample of outpatients with SCZ was related to excessive activation in regions associated with object processing and allocation of visual-spatial attention. There was no evidence for basic impairments in contour element linking in the fMRI data. The latter may be limited to poor outcome patients, where more extensive structural and functional changes in the occipital lobe have been observed.

Future clinical uses of neurophysiological biomarkers to predict and monitor treatment response for schizophrenia

Advances in psychiatric neuroscience have transformed our understanding of impaired and spared brain functions in psychotic illnesses. Despite substantial progress, few (if any) laboratory tests have graduated to clinics to inform diagnoses, guide treatments, and monitor treatment response. Providers must rely on careful behavioral observation and interview techniques to make inferences about patients' inner experiences and then secondary deductions about impacted neural systems. Development of more effective treatments has also been hindered by a lack of translational quantitative biomarkers that can span the brain-behavior treatment knowledge gap. Here, we describe an example of a simple, low-cost, and translatable electroencephalography (EEG) measure that offers promise for improving our understanding and treatment of psychotic illnesses: mismatch negativity (MMN). MMN is sensitive to and/or predicts response to some pharmacologic and nonpharmacologic interventions and accounts for substantial portions of variance in clinical, cognitive, and psychosocial functioning in schizophrenia (SZ). This measure has recently been validated for use in large-scale multisite clinical studies of SZ. Finally, MMN greatly improves our ability to forecast which individuals at high clinical risk actually develop a psychotic illness. These attributes suggest that MMN can contribute to personalized biomarker-guided treatment strategies aimed at ameliorating or even preventing the onset of psychosis.

The many faces of oxytocin: implications for psychiatry

Oxytocin is known as the 'love hormone' due its role in promoting mother-child and pair bonding. More recent research indicates that oxytocin may have broader pro-social effects on behavior and cognition, which points towards oxytocin's potential as an agent to help improve social cognition and functioning in psychiatric disorders such as schizophrenia and autism. However, new research on oxytocin has also uncovered a 'darker side', including oxytocin's possible role in social out-grouping and envy. Instead of a simple view of oxytocin as 'good' or 'bad', a more accurate depiction of oxytocin's role in social processing likely involves the presence of moderating factors. We review moderation effects in oxytocin and their implications for psychiatry. One implication is that, across diagnostic categories, oxytocin administration may have positive effects for patients with social cognitive deficits but negative effects for patients with social cognitive bias. We conclude that future intervention studies should use methods such as signal detection to measure both deficit and bias parameters of social cognition and to evaluate potential individual and contextual moderators both within and between psychiatric diagnoses in order to determine for whom oxytocin treatment may be beneficial and for whom it may actually be harmful.

Future clinical uses of neurophysiological biomarkers to predict and monitor treatment response for schizophrenia

Advances in psychiatric neuroscience have transformed our understanding of impaired and spared brain functions in psychotic illnesses. Despite substantial progress, few (if any) laboratory tests have graduated to clinics to inform diagnoses, guide treatments, and monitor treatment response. Providers must rely on careful behavioral observation and interview techniques to make inferences about patients' inner experiences and then secondary deductions about impacted neural systems. Development of more effective treatments has also been hindered by a lack of translational quantitative biomarkers that can span the brain-behavior treatment knowledge gap. Here, we describe an example of a simple, low-cost, and translatable electroencephalography (EEG) measure that offers promise for improving our understanding and treatment of psychotic illnesses: mismatch negativity (MMN). MMN is sensitive to and/or predicts response to some pharmacologic and nonpharmacologic interventions and accounts for substantial portions of variance in clinical, cognitive, and psychosocial functioning in schizophrenia (SZ). This measure has recently been validated for use in large-scale multisite clinical studies of SZ. Finally, MMN greatly improves our ability to forecast which individuals at high clinical risk actually develop a psychotic illness. These attributes suggest that MMN can contribute to personalized biomarker-guided treatment strategies aimed at ameliorating or even preventing the onset of psychosis.

F-18 fluorodeoxyglucose positron emission tomography study of impaired emotion processing in first episode schizophrenia

BACKGROUND

Schizophrenia cases have been consistently shown to have behavioural and neurofunctional abnormalities but studies during early course are scarce. The present work assesses the performance of acute first episode schizophrenia cases on correlation of a facial emotion perception task with brain function using fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET).

METHODS

Twenty First episode schizophrenia cases and 20 matched healthy controls living in the community were enrolled. For cases, longest duration of illness was one year and treatment with neuroleptic did not exceed two weeks on the day of scan. To measure facial emotion perception (FEP) both groups were administered the Emotion battery from the Penn Computerized Battery followed by PET acquisition. SPM 8 analysis for group differences at p<0.001 was performed.

RESULTS

Schizophrenia subjects showed hypoactivation of bilateral prefrontal cortices and fusiform gyrii, with significant hyperactivation of bilateral basal ganglia and left precuneus. Positive correlation of metabolism in prefrontal cortex and performance indices on emotions domain was seen. No correlation of chlorpromazine equivalent days with metabolism in basal ganglia was observed.

CONCLUSIONS

The performance of schizophrenia cases on FEP task was significantly impaired in comparison to the control group. Brain regions implicated in emotion processing showed hypometabolism in cases as compared to controls. Failure of schizophrenia cases to optimally recruit brain circuitry may be contributing to deficits on FEP task. These findings suggest inherent deficits in neural circuitry of emotion processing in schizophrenia; devoid of confounding effects of neuroleptics and duration of illness.

Developing treatments for cognitive deficits in schizophrenia: the challenge of translation

Schizophrenia is a life-long debilitating mental disorder affecting tens of millions of people worldwide. The serendipitous discovery of antipsychotics focused pharmaceutical research on developing a better antipsychotic. Our understanding of the disorder has advanced however, with the knowledge that cognitive enhancers are required for patients in order to improve their everyday lives. While antipsychotics treat psychosis, they do not enhance cognition and hence are not antischizophrenics. Developing pro-cognitive therapeutics has been extremely difficult, however, especially when no approved treatment exists. In lieu of stumbling on an efficacious treatment, developing targeted compounds can be facilitated by understanding the neural mechanisms underlying altered cognitive functioning in patients. Equally importantly, these cognitive domains will need to be measured similarly in animals and humans so that novel targets can be tested prior to conducting expensive clinical trials. To date, the limited similarity of testing across species has resulted in a translational bottleneck. In this review, we emphasize that schizophrenia is a disorder characterized by abnormal cognitive behavior. Quantifying these abnormalities using tasks having cross-species validity would enable the quantification of comparable processes in rodents. This approach would increase the likelihood that the neural substrates underlying relevant behaviors will be conserved across species. Hence, we detail cross-species tasks which can be used to test the effects of manipulations relevant to schizophrenia and putative therapeutics. Such tasks offer the hope of providing a bridge between non-clinical and clinical testing that will eventually lead to treatments developed specifically for patients with deficient cognition.